Tobacco foil and a process for its production



United States Patent 3,162,200 TOBACCO FOIL AND A PROCESS FOR ITS PRODUCTEON Ragnar Jansson, Solna, and Lars Edvin Lilia, Farsta,

Sweden, assignors to Arenco Aktiebolag, Silrtgatan, Vallingby, Sweden, a joint-stock company limited of Sweden No Drawing. Filed Nov. 27, 1962, Ser. No. 240,451 Claims priority, application Sweden, Dec. 11, 1961,

7 Claims. (Cl. 131-17) The present invention relates to a tobacco foil and more specifically to providing a water-resistant carboxymethyl cellulose foil suitable to serve as a carrier for tobacco and thereby making possible the recovery of waste products obtained in considerable quantities in the tobacco industry.

Carboxymethyl cellulose is an etherification product (ether carboxylic acid) of cellulose, obtained by the action of monochloroacetic acid on alkali treated cellulose, one or more of the hydroxylic hydrogen atoms in the glucose units of the cellulose molecules being replaced by a carboxymethyl group -CH COOH. The degree of substitution indicates the number of carboxymethyl groups that are introduced per glucose unit. The commerical carboxymethyl cellulose is marketed in the form of'its sodium salt, which is soluble in water and gives with water solutions of higher or lower viscosity according to the degree of substitution which usually varies between about 0.4 and about 1; the greater the degree of substitution the lower the viscosity. Thus by measuring the viscosity the degree of substitution can be estimated.

The use of carboxymethyl cellulose (for the sake of simplicity referred to as CMC in the following) as a carrier foil for tobacco is known, but the earlier CMC foils are impaired by several disadvantages which will be described in the following.

The CMC foil intended for use as a carrier for tobacco must meet certain demands. Thus it must be resistant to water and non-hygroscopic because a CMC foil incorporated with tobacco flour, whether it is to be used as wrappers for cigars or finely cut in the form of e.g. cigarette tobacco, must not be dissolved by the saliva. On the other hand it must not, when being stored in dry air, become brittle and show a tendency to crumble easily, but on the contrary must have a certain firmness and flexibility not only in he finished product but also so that it can be worked in tobacco machines.

Another important requirement for the use of a CMC foil as a carrier for tobacco concerns the taste of the smoke. CMC should not give the tobacco a pronounced flavour and should not give the smoke a burning or pungent taste.

The CMC tobacco foils hitherto known have in practice not fulfilled the abovementioned demands. Because of the hygroscopicity of the Na-CMC foil and its high solubility in water, Na-CMC has been converted, by acid treatment of the viscous glue used for producing the foil, into the free CMC-acid which gives a foil with suflicient wet strength.

It is known that the undesirable burning taste of the tobacco smoke is dependent on the pH of the aqueous CMC paste from which the carrier foil is produced. The opinion has previously been prevalent that the paste must be adjusted to a pH of 2.8 or less to obtain a sufiiciently water-resistant foil. It has therefore been a desideratum to convert CMC in a water-insoluble state at a higher pH. In this connection it has been suggested to treat the aqueous CMC paste with a salt of a metal the ions of which are capable of reacting with CMC and make it insoluble by forming the corresponding metal salt of CMC. However, not only are the alkali metal salts of carboxymethyl cellulose soluble but also its alkaline earth metal salts, whereby only heavy metals such as zinc, copper etc. could be considered. This method, however, is impracticable as the heavy metals not only ruin the taste of the smoke but moreover in many cases are unsanitary.

On the other hand it is known that a foil produced from Na-CMC (with a pH of approximately 7) is gradually converted into a water-resistant state and that such a foil does not form irritating products which impair the taste of the tobacco smoke. Such a conversion process demands, however, several months at room temperature and several days at temperatures up to C., so that such a course of action cannot be considered for a commercial production.

According to the present invention it has been found that a CMC carrier foil for tobacco with sufiicient wet strength can be obtained if an aqueous CMC tobacco paste is adjusted to a pH of at least 3.5 by adding a physiologically harmless acid, after which the paste is shaped to a film and the film is dried and finally aged at tempeartures between normal room temperature (20 C.) and temperatures up to C. According to the invention the CMC tobacco paste is adjusted preferably to a pH within the range of 3.6-6.

By adjusting the CMC tobacco paste to a pH which is higher than the pH for the precipitation of the pure CMC- acid but lower than the pH of the pure sodium salt of CMC, the CMC is present in the form of a mixture of the acid and the sodium salt. The sodium carboxymethyl cellulose thus acidified has then according to the inVention proved in a surprising manner to be excellently suitable as a carrier foil for tobacco.

A tobacco foil according to the invention is consequently characterised in that it contains, apart from tobacco flour and other customary additives, for instance a fire-improving agent (combustion catalyst) and a plasticizer, up to 20% and preferably 1218% carboxymethyl cellulose by weight of the dry tobacco, and a physiologically harmless acid in at the most such quantity that a 6.5 solution prepared from a newly produced watersoluble foil has a pH of 3.5 or above.

It is important to keep the lower limit for the pH (3.5) since at lower pH-values the foil, as has been mentioned, gives oil irritating products in burning. The upper limit for the pH is on the other hand not critical from this point of view but is dictated solely by the demand that the conversion process to a water-resistant condition, taking place in connection with the drying of the film at an elevated temperature, shall not require an unreasonable length of time as the advantages of the invention are not so pronounced when too little acid is added. Therefore, the foil should preferably contain the physiologically harmless acid in at least Such quantity that a 6.5% aqueous solution prepared from a newly produced foil has a pH of not more than 6.

An object of the present invention is also to provide a process for the production of a water-insoluble and waterresistant tobacco foil of the above-mentioned kind, comprising the steps of mixing and homogenizing dry, finely ground tobacco and other customary dry additives, for instance a fire-improving agent (catalyst), and thereafter dispersing the powder mixture obtained with water to form an aqueous tobacco suspension, separately producing an aqueous paste of sodium carboxymethyl cellulose and thereafter mixing and homogenizing the aqueous tobacco suspension and the aqueous paste of carboxymethyl cellulose to form an aqueous tobacco paste intended for the formation of a tobacco foil, forming said tobacco paste to a film, drying said film to a self-sustaining tobacco foil, and ageing the tobacco foil. The process is specially characterised in that a physiologically harmless acid is added to the aqueous paste of carboxymethyl cellulose or to the tobacco paste in at the most such quantity that the V tobacco paste assumes a pH of minimum 3.5 and preferably'in at least such quantity that the tobacco paste as' sumes a pH of maximum 6.

Examples of suitable physiologically harmless acids which can be used are citric, tartaric, lactic and phosphoric acid.

As stated-'abo hygroscopic and lacks the necessary wet strength, but by an ageing process the tobacco foil is converted into an insoluble state and shows thereafter the desired strength both in wet and dry states. In ageing at room temperature (20-25 C.) the transformation process can take'up to three months but can be fundamentally accelerated by heating. In ageing in air of 50 C. the transformation takes place in about 24 hours and at 100 C. in approximately 1 hour.

The drying and heat ageing are suitably carried out by means of infra-red irradiators.

Example 2.5 kg. of finely ground tobacco, of which at the most 50% by weight passed a 100 mesh sieve (0.075 mm. sieve opening), was mixed with 0.2 kg. silicon catalyst (fire improver, consisting of colloidal silica to nearly 100%). The tobacco and the catalyst were well mixed in dry condition. ml. of a 50% solution of citric acid and 450 ml. diethylene glycol (plasticizer). The dry mixture of tobacco and catalyst was well mixed into the solution obtained. 12.5 litres of a glue were. separately produced, containing 3.2% by weight sodium carboxymethyl cellulose of such a degree of substitution that a 2% solution thereof had a viscosity of approximately 900 centipoises at 25 C. The aqueous tobacco suspension with the remaining constituents was finally mixed thoroughly with sodium carboxymethyl cellulose glue, the tobacco pulp thus obtained having a pH of 4.3. v

A film approximately 0.5 mm. thick was formed from e the newly dried tobacco foil is still After that a solution of 2.5 litres of water, 450

the tobacco pulp on a polished sheet of stainless steel and then dried at an elevated temperature. The foil obtained is not water-resistant but dissolves immediately when immersed in water. In ageing at room temperature a waterresistant foil is obtained after approximately 3 months. This transformation to a water-resistant condition canbe substantially accelerated by ageingat an elevated temperature. With storage in C. air approximately 1 day is thus necessary, and at 100 C. a water-resistant foil is obtained after only approximately lhour.

Having now described the invention, what we claim as new and desire to secure by Letters Patent, is:

1. A tobacco foil made from tobacco flour, sodium carboxymethyl cellulose in an amount up to 20% by weight of the tobacco flour and an acid, said acid being present in at most such a quantity that a 6.5% aqueous solution prepared from newly produced water-soluble foil has a pH above 3.5.

2. A tobacco foil according to claim 1 wherein the acid is present in at least such a quantity thata 6.5% aqueous solution prepared from newly produced foil has a .maximum pH of '6.

3. A tobacco foil made from tobacco flour, sodium carboxymethyl cellulose in an amount 1218% by weight of the tobacco flour and an acid, said acid being present in at most such a quantity that a 6.5 aqueous solution prepared from newly produced water-soluble foil has a pH above 3.5.

4. A tobacco foil according to claim 3 wherein the acid is present in at least such a quantity that a 6.5% aqueous solution prepared from newly produced foil has a maximum pH of 6.

' 5. A tobacco foil made from tobacco flour, sodium carboxymethyl cellulose in an amount 12-18% by weight of the tobacco flour, a combustion catalyst, a plasticizer and citric acid in such as amountthat a 6.5% aqueous solution prepared from newly. produced water-soluble foil has a'pH within the range 3.5 to 6.

6. In a process for producing a tobacco foil comprising the steps of mixing and homogenizing dry, finely ground tobacco and dry additives; dispersing the resulting powder mixture with water toform an aqueous tobacco suspension; separately producing an aqueous paste of sodium carboxymethyl cellulose; mixing and homogenizing the aqueous tobacco suspension and the aqueous paste of sodiurn carboxymethyl cellulose to form an aqueous tobacco paste; forming. said aqueous tobacco paste to a film; and drying said film to. a self-sustaining tobacco" foil, the improvement which comprises adding to the aqueous paste of sodium carboxymethyl cellulose an acid in such a quantity that a 6.5 aqueous solution prepared from foil newly produced from said aqueous tobacco paste has a pH within the range 3.5 to 6.

7. In a process for producing a tobacco foil comprising the steps of mixing and homogenizing dry, finely ground tobacco and dry additives; dispersing the resulting powder mixture with water to form an aqueous tobacco suspension; separately. producing an aqueous pasteof sodium carboxymethyl cellulose; mixing and homogenizing the aqueoustobacco suspension and the aqueous'paste of sodium carboxymethyl cellulose to form an aqueous to bacco paste; forming said aqueous tobacco paste to a film; and'drying said film to-a self-sustaining tobacco foil, the improvement which comprises adding to the aqueous tobaccosuspension-an acid in such a quantity that a 6.5% aqueous solution prepared from foil newly produced from said aqueous tobacco paste has a pH within the range 3.5 to 6.

References Cited by the Examiner UNITED STATES PATENTS 2,007,407 7/35 Sadtler 131- 17 2,433,877 1/48' Wells et al. 13117 2,613,673 10/52 Sartoretto et al. 13117 2,734,510 2/56 Hungerford et al. 13l-17 2,955,601 10/60 Frankenb'erglet al. 131-17 3,000,383 9/61 Tomasi 131--17 FOREIGN PATENTS 1 1,157,608 12/57 France.

ABRAHAM G. STONE, Primary Examiner. P. RAY CHAPPELL, Examiner. 

5. A TOBACCO FIOL MADE FROM TOBACCO FLOUR, SODIUM CARBOXYMETHYL CELLULOSE IN AN AMOUNT 12-18% BY WEIGHT OF THE TOBACCO FLOUR, A COMBUSTION CATALYST, A PLASTICIZER AND CITRIC ACID IN SUCH AS AMOUNT THAT 6.5% AQUEOUS SOLUTION PREPARED FROM NEWLY PRODUCED WATER-SOLUBLE FOIL HAS A PH WITHIN THE RANGE 3.5 TO
 6. 